$ (...) .markdown is not a function

I have a problem in the compilation of mardown bootstrap editor when adapting it in angular js with a directive

function markdownEditor() {
  'ngInject';

  return {
    restrict: 'A',
    require:  'ngModel',
    link: function(scope, element, attrs, ngModel) {
      $(element).markdown({
          savable:false,
          onChange: function(e){
            ngModel.$setViewValue(e.getContent());
          }
        });

    }
  };
}

export default markdownEditor;

When compiling the directive I get the following error

  

$ (...). markdown is not a function

Without compiling the files everything works great and the editor shows me without any problem